Murray's Work on Distribution 325 
are now quite separate, have been continuously, or almost con- 
tinuously, united with each other, and with the many existing oceanic 
islands’.” Again, “believing...that our continents have long remained 
in nearly the same relative position, though subjected to large, but par- 
tial oscillations of level,” that means to say within the period of existing 
species, or “within the recent period.” The difficulty was to a great 
extent one of hisown making. Whilst almost everybody else believed 
in the immutability of the species, which implies an enormous age, 
logically since the dawn of creation, to him the actually existing 
species as the latest results of evolution, were necessarily something 
very new, so young that only the very latest of the geological epochs 
could have affected them. It has since come to our knowledge that 
a great number of terrestrial “recent” species, even those of the 
higher classes of Vertebrates, date much farther back than had been 
thought possible. Many of them reach well into the Miocene, a 
time since which the world seems to have assumed the main outlines 
of the present continents. 
In the year 1866 appeared A. Murray’s work on the Geographical 
Distribution of Mammals, a book which has perhaps received less 
recognition than it deserves. His treatment of the general intro- 
ductory questions marks a considerable advance of our problem, 
although, and partly because, he did not entirely agree with Darwin’s 
views as laid down in the first edition of The Origin of Species, 
which after all was the great impulse given to Murray’s work. Like 
Forbes he did not shrink from assuming enormous changes in the 
configuration of the continents and oceans because the theory of 
descent, with its necessary postulate of great migrations, required 
them. He stated, for instance, “that a Miocene Atlantis sufficiently 
explains the common distribution of animals and plants in Europe 
and America up to the glacial epoch.” And next he considers how, 
and by what changes, the rehabilitation and distribution of these 
lands themselves were effected subsequent to that period. Further, 
he deserves credit for having cleared up a misunderstanding of the 
idea of specific centres of creation. Whilst for instance Schmarda 
assumed without hesitation that the same species, if occurring at 
places separated by great distances, or by apparently insurmountable 
barriers, had been there created independently (multiple centres), 
Lyell and Darwin held that each species had only one single centre, 
and with this view most of us agree, but their starting point was 
to them represented by one individual, or rather one single pair. 
According to Murray, on the other hand, this centre of a species is 
formed by all the individuals of a species, all of which equally undergo 
those changes which new conditions may impose upon them. In this 
respect a new species has a multiple origin, but this in a sense very 
1 Ibid. p. 357. ° Ibid. p. 370, 
